Device for ejecting in injection molding of threaded articles

ABSTRACT

A method for ejecting in injection molding of threaded articles wherein a movable mold clamping plate is provided with a shaft adapted to rotate threaded cores and a plurality of rods movably supporting a stripper plate arranged around said cores, thus permitting to release threaded molded articles from the cores by rotation thereof and forward movement of said stripper plate after mold opening, said forward movement being realized under pressure of the oil forced into the rods simultaneously with revolution of the rotating shaft, said stripper plate being moved at a velocity corresponding to the lead of screw thread of the cores by a combined action of a cam adapted to be actuated synchronously with the cores by revolution of said rotating shaft to me in one direction, said cam being set at a desired angle, and a stylus provided in contact with said model cam at the rear of said rods.

il'ited States Patent H91 3,712,786

Aolri 51 Jan. 23, 1973 [54] DEVICE FOR EJECTING IN INJECTION MOLDING OFTHREADED ARTICLES [76] Inventor: Katashi Aoki, 6037, Oaza Minamijo,Sakaki-machi, Hanishina-gun, Nagano-ken, Japan [22] Filed: Feb. 3, 1971[21] Appl. No.: 112,225

Primary Examiner-J. Spencer Overholser Assistant Examiner-David S.Safran Attorney-David H. Semmes 5 7 ABSTRACT A method for ejecting ininjection molding 'of threaded articles wherein a movable mold clampingplate is provided with a shaft adapted to rotate threaded cores and aplurality of rods movably sup- [30] Foreign Applicafion Priority Damporting a stripper plate arranged around said cores, Feb.4, 1970 Japan..45/9439 thus Permitting release threaded "wlded articles from thecores by rotation thereof and forward move- 52 us. Cl. ..425/438 425/165264/318 of Said Stripper plate fter mold Opening, said ['51] Int Cl; n1/14 forward movement being realized under pressure of [58] Field ofsemlch 18/2 425/161 the oil forced into the rods simultaneously with425/165 revolution of the rotating shaft, said stripper plate Y beingmoved at a velocity corresponding to the lead of R C d screw thread ofthe cores by a combined action of a 1 everences v cam adapted to beactuated synchronously with the UNITED STATES PATENTS cores byrevolution of said rotating shaft to me in one direction, said cam beingset at a desired angle, and a 3,388,431 6/1968 Aoki ..l8/2 RS X tylurovided in ontact with said model cam at the Wilson X rear of said rods2,984,862 5/1961 Chabotte... ..l8/2 RS 2,718,032 9/1955 Harvey ..l8/2 RS5 Claims, 5 Drawing Figures i p y 42- PATENTEDJAH23'1915 3.712.786

sum 3 or 3 I INVENTOR- #010 WM MM DEVICE FOR ILIIEIC'IIllGv IN INJECTIONMOLDING F THREADED ARTICLES The present invention relates to methods anddevices for ejecting molded articles (mold releasing) to be used ininjection molding of articles having screw threaded portions such asscrew caps of bottles, joints and the like.

An injection molding machine designed to produce threaded articlesincludes a thread ejecting device associated with the mold closingmechanism thereof. This ejecting device is operated during the moldopening step. Turning force of the motor reduced by a worm gear istransmitted to a thread attachment and further to a gear box to rotate acore. In this case, the molded articles cannot be smoothly ejected fromthe mold by the revolution of the core only. In view of this fact, saidthread attachment is connected to a stripper plate so that the stripperplate is moved at a velocity corresponding to the lead of screw threadof the core to achieve complete release of the molded article from thecore. Accordingly, the core and the thread attachment have suchrelationship that incorrect selection of thelatter at the time ofmounting the former not only makes it impossible to eject the moldedarticle but also leads to the damage thereof. Moreover, such arrangementis disadvantageous in that in order to move the stripper plate by thethread attachment it is necessary to operate the thread attachmentbefore mold closing so as to move the stripper plate back to the gearbox.

It is an object of this invention to provide a method to be used ininjection molding of threaded articles for ejecting products made ofsynthetic resins having threaded portions smoothly and securely withoutemploying any thread attachment.

It is another object of this invention to provide a method to be used ininjection molding for ejecting the molded articles of synthetic resinshaving threaded portions wherein mold closing can be realized by leavinga stripper plate thrust out for ejecting molded articles in that statewithout moving it back to its position.

It is still another object of this invention to provide a device to beused in injection molding of threaded articles for ejecting wherein astripper plate can be moved at a velocity corresponding to the lead ofscrew thread of a core by adjusting to the pitch of screw thread theangle of a cam arranged in a position related to a rotating shaftwithoutreplacing other parts regardless of the difference which takes placewith the replacement of molds in the pitch of screw thread made on thecircumference of the core and also in the degree of removal of themolded article from the mold per one revolution of the core.

In order to afford a clearer understanding of the presentinvention'reference will now be made to the accompanying drawingsillustrating by way of example a typical embodiment of the invention. Inthe drawings:

FIG. 1 shows a plan in cross-section of the device of this invention atthe time of mold opening;

FIG. 2 shows a plan in cross-section of the device of this invention atthe time of ejecting;

FIG. 3 shows a plan in cross-section of the deviceof this invention atthe time of fast feed;

FIG. 4 shows a plan in cross-section of the device of this invention atthe time of mold closing; and

FIG. 5 is a vertical sectional view of the control means.

Referring now to the drawings, the reference numeral 11 designates afixed mold and 12 indicates cores suitable to enter into the fixed mold11 and having male threads 13 cut on outside surfaces in the endportions thereof. The fixed mold 11 is secured by bolts or the like to afixed mold support plate 14 in a through hole 15 of which an injectionnozzle A is located.

The above cores project from a gear box 17 detachably mounted in frontof a movable mold clamp ing plate 16 which is supported by tie-bars 10.In this gear box is provided with an interlocking gear group consistingof a gear 18 and a number of pinions 19 equal to the number of cores 12arranged around the gear 18. The main shaft 26 of the gear 18 is soconnected to a rotating shaft 21 made integral with a worm gear 22 thatthe rotating shaft 21 and the gear 18 rotate in a fixed direction withthe rotation of a worm gear 24 of driving shaft 23 connected to a motor.Their rotating force is transmitted to each pinion 19 and the core 12having the same axis therewith, respectively.

In front of the gear box 17 is arranged a stripper plate 25 havingthrough holes through which cores 12 pass. To both ends of this stripperplate 25 are connected through joints 30 the rods 29 each made integralwith a head 28 which operates in a hydraulic cylinder 27 provided in themoving mold clamping plate 16. The back ends of rods 29 are integrallyconnected to each other by a connecting member 32 having a hydraulicservovalve 31 inwardly projecting therin. In this hydraulic servo-valve32 is provided a valve 34 adapted to act resiliently by a spring 33 andthe end exposed outside of which constitutes a stylus 35. By the numeral36 is designated a means for controlling the movement of the stripperplate which is connected integrally to the moving mold clamping plate 16and located between the moving mold clamping plate 16 and the hydraulicservo-valve 31. This movement control means 36 consists of a combinationof a fixed frame 37 and-a movable plate 38. On the fixed frame 37 isprovided a pinion 40 connected through an electromagnetic clutch 39 tothe rotating shaft 21, and on the movable plate 38 are arranged in thesame direction a rack 41 adapted to engage with the pinion 40 and aL-shaped adjustable cam 42 adapted to contact the stylus 35 of thehydraulic servo-valve 31. The angle of inclination of the cam 42 can befreely adjustable with its one end so fixed by a shaft 43 as to act as afulcrum. By 44 is indicated a guide groove provided on the other end ofthe cam 42 and by 45 a fastener.

Next, in a hydraulic circuit 46 connecting the hydraulic cylinders 27 tothe hydraulic servo-valve 31 is provided a hydraulic device 47. Theworking oil is supplied through the hydraulic servo-valve 31 and thehydraulic device 47 to both hydraulic cylinders 27 and actuates the rods29 to cause the stripper plate 25 to move forward.

. In the ejecting device having the above construction, since to thefront end of the rotating shaft 21 is connected, the gear 18 adapted torotate each core 12 and to the other end thereof the pinion 40 of themovement control means 36 through the medium of the electromagneticclutch 39, the cores l2 and the movable plate 38 can be simultaneouslyoperated by the revolution of the rotating shaft 21. When the movableplate 38 is actuated by the action of the pinion 40 and the rack 41 tomove in one direction, the stylus 35 adapted to contact the cam 42 movesforward along a slope changing its position, thereby causing thestripper plate 25 to move forward in the mold releasing direction bymeans of the rods 29 integrally connected thereto. Accordingly, once theangle of inclination of the cam 42 has been adjusted so as to be equalto the pitch of screw thread of the cores 12, the stripper plate 25 willbe able to move at a velocity corresponding to the lead of screw threadof the cores.

From the above description it will be seen how the mold releasing deviceof this invention is constructed. Further, its operation and action willbe described hereinafter. The injection molding process is roughlydivided into the following operations and proceeds in the followingorder: Mold clamping injection cooling mold opening revolution of coresand advance of stripper plate ejecting of molded article mold closingmold clamping.

Referring to FIGS. 1, 2, 3 and 4, FIG. 1 shows the mold opening in whichthe mold is in a open state. At this time a switch is actuated so thatthe driving shaft 23 connected to the motor causes the rotating shaft 21by the aid of the worm 24 and the worm gear 22 to rotate in thedirection indicated by the arrow. The rotating shaft 21 rotates thecores 12 in a fixed direction through the medium of the electromagneticclutch 39 and the gear group consisting of the gear and pinions. As aresult of this an action to remove the molded article designated by Boccurs in the positions of the cores 12 as shown in FIG. 2 andsimultaneously the movable plate 38 in the control means 36 movesthereby causing the stripper plate 25 to move forward by a combinedaction of the cam 42, stylus 35 and rods 29. The movement of saidstripper plate 25 results from the action of the working oil forcedthrough the hydraulic servovalve 31 to the hydraulic cylinders 27.Accordingly, since the quantity of oil supplied thereto is controlled bythe hydraulic servo-valve 31 and the stylus 35 of this hydraulicservo-valve 3l-contacts the cam 42 the angle of inclination of which hasbeen adjusted to be equal to the pitch of screw thread of the cores 12,the stripper plate 25 moves at a velocity corresponding to the lead ofscrew thread of the cores thus permitting to reliably remove the moldedarticle B from the mold.

When the releasing of the molded article B is recognized, the moldclosing operation is started as shown in FIG. 3 and the motor is stoppedby actuating the switch. And the electromagnetic clutch 39 is released,the movable plate 38 is put in its free state and at the same time thehydraulic circuit is shut off in the hydraulic device 47. As a result ofthis the hydraulic resistance in each hydraulic cylinder 27 is relieved,and the movable plate 38 immediately after having been in its free statemoves back to its original position, forcing in the stylus 35, under theaction of the weight C hung on its back side. Further, when the movingmold clamping plate 16 is moved forward for the purpose of moldclamping, the stripper plate 25 remained in its advanced position ispushed back together with the rods 29 by the fixed mold 11 therebyurging the stylus 35 again toward its former projected position (referto FIG. 4). After the mold closing and clamping has thus been completed,synthetic resin is injected into the mold cavity in the usual manner,and after the molding and cooling the mold opening is carried out in thestate indicated in FIG. 1.

From the foregoing it will be apparent that the mold closing and openingmechanism according to the method of this invention is simplified ascompared with those according to conventional methods by reason of thefact that the latter requires a control screw, while in this invention,as mentioned above, to a shaft rotating cores is connected a controlmeans provided with a movable plate made integral with a cam in such amanner that saidmovable plate moves with the rotation of cores therebycausing a stripper plate to move forward at a velocity corresponding tothe lead of screw thread of cores. Moreover, the moving speed of thestripper plate can be regulated by adjusting the cam even if the pitchof screw thread of cores is changed since the angle of inclination ofthe cam can be adjusted so as to be equal to the pitch of screw threadmade on the circumference of cores. Furthermore, according toconventional methods the stripper plate projected to eject the moldedarticle from the mold needs to be moved back to its original positionbecause of the use of control screw while in this invention the moldclosing can be realized leaving the stripper plate as it is since thestripper plate can be put in a free position. Accordingly, the moldingoperation according to the method of the present invention can be easilyand rapidly accomplished compared with those of conventional methods,which constitutes many advantages of the method of this invention.

What is claimed is:

l. A device for ejecting in injection molding of threaded articlescomprising a fixed mold provided on a fixed mold retaining plate andthreaded cores installed on a moving mold clamping plate, said movingmold clamping plate having therein a rotating shaft, connected directlyor through the medium of a gear to said cores, a plurality of rodsmovably supporting a stripper plate arranged around said cores and acylinder urging said rods to move forward and backward, to the back endof said rotating shaft being connected, through the medium of a memberconverting rotary motion into rectilinear movement, a rectilinearlymovable plate provided with a cam the angle of inclined of which can beadjusted to be equal to the pitch of screw thread of said cores andmovable with said movable plate, and at the rear of said rods beingprovided a stylus in contact with said cam, and adapted to adjustforward movement of said rods and stripper plate to the lead of screwthread of said cores through activation of said cylinder upon movementof said cam with said plate upon rotation of said rotating shaft.

2. A device as set forth in claim 1 wherein the stylus at the rear ofsaid rods supporting said stripper plate is made integral with a valveprovided in a hydraulic servo-valve.

3. A device as set forth in claim 1 wherein a driving portion of saidmovable plate provided with said cam is connected through anelectromagnetic clutch to said rotating shaft provided in said movingmold clamping plate.

for controlling movement of said stripper plate comprising such drivingmembers as said movable plate, said cam, a pinion and a rack is providedwith a weight hung in a suitable position to force said movable plate,when said control means is disconnected from said rotating shaft after amolding is released from the mold, to slide along a fixed frame into itsoriginal position.

* 1k t t

1. A device for ejecting in injection molding of threaded articlescomprising a fixed mold provided on a fixed mold retaining plate andthreaded cores installed on a moving mold clamping plate, said movingmold clamping plate having therein a rotating shaft, connected directlyor through the medium of a gear to said cores, a plurality of rodsmovably supporting a stripper plate arranged around said cores and acylinder urging said rods to move forward and backward, to the back endof said rotating shaft being connected, through the medium of a memberconverting rotary motion into rectilinear movement, a rectilinearlymovable plate provided with a cam the angle of inclined of which can beadjusted to be equal to the pitch of screw thread of said cores andmovable with said movable plate, and at the rear of said rods beingprovided a stylus in contact with said cam, and adapted to adjustforward movement of said rods and stripper plate to the lead of screwthread of said cores through activation of said cylinder upon movementof said cam with said plate upon rotation of said rotating shaft.
 2. Adevice as set forth in claim 1 wherein the stylus at the rear of saidrods supporting said stripper plate is made integral with a valveprovided in a hydraulic servo-valve.
 3. A device as set forth in claim 1wherein a driving portion of said movable plate provided with said camis connected through an electromagnetic clutch to said rotating shaftprovided in said moving mold clamping plate.
 4. A device as set forth inclaim 1 wherein the cam on said movable plate has one end thereof fixedby a shaft on said movable plate so as to be set at an anglecorresponding to the lead of screw thread of cores to be used in moldingand the free end thereof shaped so as to be fixed at a desired angle andprovided with a fastening member.
 5. A device as set forth in claim 1wherein a means for controlling movement of said stripper platecomprising such driving members as said movable plate, said cam, apinion and a rack is provided with a weight hung in a suitable positionto force said movable plate, when said control means is disconnectedfrom said rotating shaft after a molding is released from the mold, toslide along a fixed frame into its original position.